Integrated water resource management (IWRM) has long been advocated in academia and politics but appears difficult to pursue in practice. Defenders of IWRM call for governance institutions adapted to hydrological boundaries, but these would be at odds with existing administrative ones. In this paper, we investigate how coordination platforms at sub‐basin scale can contribute to IWRM. Most IWRM literature focuses on the catchment scale. It is however acknowledged by several authors that coordination is also needed at a lower level. Through document analysis and semi‐structured interviews, a comparison is made of the Flemish sub‐basin boards and the Walloon river contracts, two types of coordination platform in different regions of Belgium. Belonging to the same federal state, they form valuable cases to compare divergent systems rooted in similar administrative settings. A number of key factors appear to contribute to the effectiveness of the coordination platforms, as it is perceived by their stakeholders. These factors are a clear but flexible legislative framework, (financial) support of a higher government rather than command‐and‐control steering, the personal commitment of their coordinators, an independent status of their staff, a sense of urgency and a good connection with civil society and the wider public. Copyright © 2017 John Wiley & Sons, Ltd and ERP Environment